MCP Server: SSH Rails Runner

An MCP server that enables secure remote execution of Rails console commands via SSH. This server provides tools for both read-only operations and carefully managed mutations in a deployed Rails environment.

This works great with Cursor. You can use Cursor Composer to pull in your Rails model files as context and then use the execute_read_only, dry_run_mutate, and execute_mutate tools to make changes to the database. No need to trudge through complicated Admin UI's to get your data wrangling and analysis done.

Example

!Example

Features

- Remote Rails console execution over SSH
- Safe read-only operations
- Dry-run capability for mutations
- Execution of approved mutations
- Resource management for code snippets

Installation

``bash
npm install
npm run build
`

Configuration

Set the following environment variables:

`bash
SSH_HOST=your.remote.host
SSH_USER=your_ssh_user
SSH_PRIVATE_KEY_PATH=your_SSH_PRIVATE_KEY_PATH
RAILS_WORKING_DIR=/path/to/rails/app
`

Usage with Claude Desktop

Add to your Claude Desktop configuration:

`json
{
"mcpServers": {
"ssh-rails-runner": {
"command": "npx",
"args": ["mcp-server-ssh-rails-runner"],
"env": {
"SSH_HOST": "your.remote.host",
"SSH_USER": "your_ssh_user",
"SSH_PRIVATE_KEY_PATH": "your_SSH_PRIVATE_KEY_PATH",
"RAILS_WORKING_DIR": "/path/to/rails/app/root",
"PROJECT_NAME_AS_CONTEXT": "Name that shows up in tool descriptions to help the LLM describe what kind of Rails project we're working with.",
"CODE_SNIPPET_FILE_DIRECTORY": "/path/to/store/code/snippets/locally"
}
}
}
}
`

If CODE_SNIPPET_FILE_DIRECTORY is not provided, snippets will be stored in a temporary directory (e.g., /tmp/mcp-ssh-rails-runner-code-snippets).
PROJECT_NAME_AS_CONTEXT is optional and helps identify the project context in tool descriptions.

Available Tools

The server now uses a Prepare -> Execute workflow:

$3

- Arguments: name (string, for filename), type (enum: "readOnly" | "mutate"), code (string, Ruby code), description (string, optional).
- Function: Saves the provided Ruby code to a local file named code_snippet_.json, marks it as read-only or mutate, and opens the file for review.
- Returns: The file:// URI of the created snippet.

$3

- Arguments: uri (string, file:// URI from prepareCodeSnippet).
- Function: Reads the code snippet from the URI, verifies it's marked as readOnly, performs a safety check on the code, and executes it.
- Returns: The output of the Rails command.

$3

- Arguments: uri (string, file:// URI from prepareCodeSnippet).
- Function: DANGER ZONE! Reads the code snippet, verifies it's marked as mutate, and executes it directly. There is no dry run or further safety check within this tool.
- Returns: The output of the Rails command.
- Usage: ONLY CALL THIS AFTER THE USER HAS REVIEWED the prepared code (via the opened file from prepareCodeSnippet) AND EXPLICITLY CONFIRMED they want to execute the mutation.

Security Considerations

- Only use with trusted SSH endpoints from your own local machine that is (temporarily) provided access to the remote environment.
- Crucially, always review the code saved by prepareCodeSnippet before executing any mutation with executeCodeSnippetMutate`. The responsibility for confirming mutations lies with the user and the calling AI.

License

MIT